model.cc

   1 #include <stdio.h>
   2
   3 #include "model.h"
   4 #include "action.h"
   5 #include "tree.h"
   6 #include "schedule.h"
   7 #include "common.h"
   8
   9 #define INITIAL_THREAD_ID       0
  10
  11 ModelChecker *model;
  12
  13 ModelChecker::ModelChecker()
  14 {
  15         /* First thread created will have id INITIAL_THREAD_ID */
  16         this->next_thread_id = INITIAL_THREAD_ID;
  17         used_sequence_numbers = 0;
  18         /* Initialize default scheduler */
  19         this->scheduler = new Scheduler();
  20
  21         num_executions = 0;
  22         this->current_action = NULL;
  23         this->exploring = NULL;
  24         this->nextThread = THREAD_ID_T_NONE;
  25
  26         rootNode = new TreeNode(NULL);
  27         currentNode = rootNode;
  28         action_trace = new action_list_t();
  29 }
  30
  31 ModelChecker::~ModelChecker()
  32 {
  33         delete action_trace;
  34         delete this->scheduler;
  35         delete rootNode;
  36 }
  37
  38 void ModelChecker::reset_to_initial_state()
  39 {
  40         DEBUG("+++ Resetting to initial state +++\n");
  41         std::map<int, class Thread *>::iterator it;
  42         for (it = thread_map.begin(); it != thread_map.end(); it++)
  43                 delete (*it).second;
  44         thread_map.clear();
  45         action_trace = new action_list_t();
  46         currentNode = rootNode;
  47         current_action = NULL;
  48         next_thread_id = INITIAL_THREAD_ID;
  49         used_sequence_numbers = 0;
  50         /* scheduler reset ? */
  51 }
  52
  53 thread_id_t ModelChecker::get_next_id()
  54 {
  55         return next_thread_id++;
  56 }
  57
  58 int ModelChecker::get_next_seq_num()
  59 {
  60         return ++used_sequence_numbers;
  61 }
  62
  63 Thread * ModelChecker::schedule_next_thread()
  64 {
  65         Thread *t;
  66         if (nextThread == THREAD_ID_T_NONE)
  67                 return NULL;
  68         t = thread_map[id_to_int(nextThread)];
  69         if (t == NULL)
  70                 DEBUG("*** error: thread not in thread_map: id = %d\n", nextThread);
  71         return t;
  72 }
  73
  74 /*
  75  * get_next_replay_thread() - Choose the next thread in the replay sequence
  76  *
  77  * If we've reached the 'diverge' point, then we pick a thread from the
  78  *   backtracking set.
  79  * Otherwise, we simply return the next thread in the sequence.
  80  */
  81 thread_id_t ModelChecker::get_next_replay_thread()
  82 {
  83         ModelAction *next;
  84         thread_id_t tid;
  85
  86         next = exploring->get_state();
  87
  88         if (next == exploring->get_diverge()) {
  89                 TreeNode *node = next->get_node();
  90
  91                 /* Reached divergence point; discard our current 'exploring' */
  92                 DEBUG("*** Discard 'Backtrack' object ***\n");
  93                 tid = node->getNextBacktrack();
  94                 delete exploring;
  95                 exploring = NULL;
  96         } else {
  97                 tid = next->get_tid();
  98         }
  99         DEBUG("*** ModelChecker chose next thread = %d ***\n", tid);
 100         return tid;
 101 }
 102
 103 thread_id_t ModelChecker::advance_backtracking_state()
 104 {
 105         /* Have we completed exploring the preselected path? */
 106         if (exploring == NULL)
 107                 return THREAD_ID_T_NONE;
 108
 109         /* Else, we are trying to replay an execution */
 110         exploring->advance_state();
 111         if (exploring->get_state() == NULL)
 112                 DEBUG("*** error: reached end of backtrack trace\n");
 113
 114         return get_next_replay_thread();
 115 }
 116
 117 bool ModelChecker::next_execution()
 118 {
 119         DBG();
 120
 121         num_executions++;
 122         print_summary();
 123         if ((exploring = model->get_next_backtrack()) == NULL)
 124                 return false;
 125         model->reset_to_initial_state();
 126         nextThread = get_next_replay_thread();
 127
 128         if (DBG_ENABLED()) {
 129                 printf("Next execution will diverge at:\n");
 130                 exploring->get_diverge()->print();
 131                 print_list(exploring->get_trace());
 132         }
 133         return true;
 134 }
 135
 136 ModelAction * ModelChecker::get_last_conflict(ModelAction *act)
 137 {
 138         action_type type = act->get_type();
 139
 140         switch (type) {
 141                 case THREAD_CREATE:
 142                 case THREAD_YIELD:
 143                 case THREAD_JOIN:
 144                         return NULL;
 145                 case ATOMIC_READ:
 146                 case ATOMIC_WRITE:
 147                 default:
 148                         break;
 149         }
 150         /* linear search: from most recent to oldest */
 151         action_list_t::reverse_iterator rit;
 152         for (rit = action_trace->rbegin(); rit != action_trace->rend(); rit++) {
 153                 ModelAction *prev = *rit;
 154                 if (act->is_dependent(prev))
 155                         return prev;
 156         }
 157         return NULL;
 158 }
 159
 160 void ModelChecker::set_backtracking(ModelAction *act)
 161 {
 162         ModelAction *prev;
 163         TreeNode *node;
 164
 165         prev = get_last_conflict(act);
 166         if (prev == NULL)
 167                 return;
 168
 169         node = prev->get_node();
 170
 171         /* Check if this has been explored already */
 172         if (node->hasBeenExplored(act->get_tid()))
 173                 return;
 174         /* If this is a new backtracking point, mark the tree */
 175         if (node->setBacktrack(act->get_tid()) != 0)
 176                 return;
 177
 178         DEBUG("Setting backtrack: conflict = %d, instead tid = %d\n",
 179                         prev->get_tid(), act->get_tid());
 180         if (DBG_ENABLED()) {
 181                 prev->print();
 182                 act->print();
 183         }
 184
 185         Backtrack *back = new Backtrack(prev, action_trace);
 186         backtrack_list.push_back(back);
 187 }
 188
 189 Backtrack * ModelChecker::get_next_backtrack()
 190 {
 191         Backtrack *next;
 192         if (backtrack_list.empty())
 193                 return NULL;
 194         next = backtrack_list.back();
 195         backtrack_list.pop_back();
 196         return next;
 197 }
 198
 199 void ModelChecker::check_current_action(void)
 200 {
 201         ModelAction *next = this->current_action;
 202
 203         if (!next) {
 204                 DEBUG("trying to push NULL action...\n");
 205                 return;
 206         }
 207         current_action = NULL;
 208         nextThread = advance_backtracking_state();
 209         next->set_node(currentNode);
 210         set_backtracking(next);
 211         currentNode = currentNode->exploreChild(next->get_tid());
 212         this->action_trace->push_back(next);
 213 }
 214
 215 void ModelChecker::print_summary(void)
 216 {
 217         printf("\n");
 218         printf("Number of executions: %d\n", num_executions);
 219         printf("Total nodes created: %d\n", TreeNode::getTotalNodes());
 220
 221         scheduler->print();
 222
 223         print_list(action_trace);
 224         printf("\n");
 225
 226 }
 227
 228 void ModelChecker::print_list(action_list_t *list)
 229 {
 230         action_list_t::iterator it;
 231
 232         printf("---------------------------------------------------------------------\n");
 233         printf("Trace:\n");
 234
 235         for (it = list->begin(); it != list->end(); it++) {
 236                 (*it)->print();
 237         }
 238         printf("---------------------------------------------------------------------\n");
 239 }
 240
 241 int ModelChecker::add_thread(Thread *t)
 242 {
 243         thread_map[id_to_int(t->get_id())] = t;
 244         scheduler->add_thread(t);
 245         return 0;
 246 }
 247
 248 void ModelChecker::remove_thread(Thread *t)
 249 {
 250         scheduler->remove_thread(t);
 251 }
 252
 253 int ModelChecker::switch_to_master(ModelAction *act)
 254 {
 255         Thread *old;
 256
 257         DBG();
 258         old = thread_current();
 259         set_current_action(act);
 260         old->set_state(THREAD_READY);
 261         return Thread::swap(old, get_system_context());
 262 }
 263
 264 ModelAction::ModelAction(action_type_t type, memory_order order, void *loc, int value)
 265 {
 266         Thread *t = thread_current();
 267         ModelAction *act = this;
 268
 269         act->type = type;
 270         act->order = order;
 271         act->location = loc;
 272         act->tid = t->get_id();
 273         act->value = value;
 274         act->seq_number = model->get_next_seq_num();
 275 }
 276
 277 bool ModelAction::is_read()
 278 {
 279         return type == ATOMIC_READ;
 280 }
 281
 282 bool ModelAction::is_write()
 283 {
 284         return type == ATOMIC_WRITE;
 285 }
 286
 287 bool ModelAction::is_acquire()
 288 {
 289         switch (order) {
 290         case memory_order_acquire:
 291         case memory_order_acq_rel:
 292         case memory_order_seq_cst:
 293                 return true;
 294         default:
 295                 return false;
 296         }
 297 }
 298
 299 bool ModelAction::is_release()
 300 {
 301         switch (order) {
 302         case memory_order_release:
 303         case memory_order_acq_rel:
 304         case memory_order_seq_cst:
 305                 return true;
 306         default:
 307                 return false;
 308         }
 309 }
 310
 311 bool ModelAction::same_var(ModelAction *act)
 312 {
 313         return location == act->location;
 314 }
 315
 316 bool ModelAction::same_thread(ModelAction *act)
 317 {
 318         return tid == act->tid;
 319 }
 320
 321 bool ModelAction::is_dependent(ModelAction *act)
 322 {
 323         if (!is_read() && !is_write())
 324                 return false;
 325         if (!act->is_read() && !act->is_write())
 326                 return false;
 327         if (same_var(act) && !same_thread(act) &&
 328                         (is_write() || act->is_write()))
 329                 return true;
 330         return false;
 331 }
 332
 333 void ModelAction::print(void)
 334 {
 335         const char *type_str;
 336         switch (this->type) {
 337         case THREAD_CREATE:
 338                 type_str = "thread create";
 339                 break;
 340         case THREAD_YIELD:
 341                 type_str = "thread yield";
 342                 break;
 343         case THREAD_JOIN:
 344                 type_str = "thread join";
 345                 break;
 346         case ATOMIC_READ:
 347                 type_str = "atomic read";
 348                 break;
 349         case ATOMIC_WRITE:
 350                 type_str = "atomic write";
 351                 break;
 352         default:
 353                 type_str = "unknown type";
 354         }
 355
 356         printf("(%4d) Thread: %d\tAction: %s\tMO: %d\tLoc: %14p\tValue: %d\n",
 357                         seq_number, id_to_int(tid), type_str, order, location, value);
 358 }